C3 Hardness of Water

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  • Created by: Théa
  • Created on: 18-05-13 18:41

What makes water hard?

-MAGNESIUM and CALCIUM IONS cause the hardness of water

-Hard water contains these compunds, which react with soap to form SCUM, however modern 'soapless detergents' do not produce scum in hard water

-The magnesium and calcium get into the water by dissolving when the water flows over rocks containing these compounds

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Problems of Hard Water

Scale Formation

-Hard water produces solid insoluble limescale (CaCO3) when heated

-Forms in washing machines, immersion heaters, kettles, etc

-More energy is required to heat things, as the scale creates an insulating layer

Expensive

-Soap is wasted, reacting with ions, so more is needed to get a good lather

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Advantages of Hard Water

-Calcium is good for healthy teeth and bones

-Studies have shown that people who live in areas with hard water have less risk of developing heart disease, probably due to the minerals in the water

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Softening Hard Water - Temporary

-Temporary Hardness is caused by hydrogencarbonate ions (HCO3 -)

-It can be removed by boiling, which causes the hydrogencarbonate to decompose

-However this gives scale

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Softening Hard Water - Permanent

-Permanent water hardness is caused by calcium sulphate (plus some other things)

-It can be removed by adding 'washing soda', which is sodium carbonate

-Or, it can also be removed by running water through 'ion exchange columns'

-Both these methods also work for removing temporary hardness as well

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Softening Hard Water

Disadvantages:

-Sodium ions which replace the ions removed in the ion exchange columns can cause high blood pressure

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